JP6135082B2 - Induction heating furnace - Google Patents

Description

  The present invention relates to an induction heating furnace that heats a heating object disposed in a heating chamber.

  Recently, silicon carbide (SiC) semiconductors have attracted attention as devices that can realize small and low-loss semiconductor devices that surpass silicon (Si) semiconductors due to their excellent physical and chemical properties. .

  When the quality of the epitaxial wafer used for the production of this SiC semiconductor device (hereinafter sometimes referred to as “SiC semiconductor”) is not sufficient, it is difficult to produce a chip having a predetermined area, particularly a large area chip, This can be a significant barrier to the practical application of high-current devices that demonstrate the usefulness of the material properties of SiC.

  Here, the epitaxial wafer is a single crystal SiC thin film (also referred to as a SiC epitaxial film) whose thickness and impurity concentration are precisely controlled on the surface of a high-quality wafer. A high quality and uniform epitaxial growth technique on a large (large diameter) wafer is required.

As a method of forming a SiC thin film on a wafer, CVD (Chemical
Vapor Deposition (Chemical Vapor Deposition) method has been adopted, and an epitaxy apparatus used for this method has been developed (for example, Patent Document 1).

  Patent Document 1 discloses an epitaxial growth chamber main body mainly composed of a quartz tube having a constant thickness, a coil disposed in a spiral shape around the outer wall of the epitaxial growth chamber main body, and an epitaxial growth chamber main body that is made of a conductive material. A cylindrical heat insulating material provided inside the tube, a cylindrical first susceptor made of graphite arranged inside the heat insulating material, and a cylindrical second material made of graphite arranged inside the first susceptor. There has been disclosed a CVD epitaxial apparatus including a susceptor and configured to be capable of disposing a SiC wafer inside a second susceptor.

  In this CVD epitaxial apparatus, the first susceptor is directly heated by causing a current to flow through the coil to generate a high frequency, and the second susceptor is indirectly heated by heating the first susceptor (heat conduction and radiation from the first susceptor). By being heated, the epitaxial growth for forming the SiC thin film on the wafer in the second susceptor is realized.

  That is, the second susceptor that heats and accommodates the SiC wafer that is the object to be heated accommodated therein functions as a heating chamber, and the first susceptor that heats the heating chamber by generating heat functions as a heating element.

  On the other hand, the present applicant, for example, includes an induction heating furnace that heats and melts the metal material in the furnace body by housing the metal material inside the furnace body and heating the induction heating coil wound around the outside of the furnace body. It has been developed and patent applications have been filed so far (for example, Patent Document 2). Here, the “furnace body” functions as a heating chamber for heating the metal material.

  The present applicant has repeatedly studied to realize epitaxial growth in which a SiC thin film is formed on a wafer in a heating chamber by applying a technique related to an induction heating furnace to an epitaxial apparatus.

JP 2005-109408 A JP 2010-17749 A

  By the way, in above-mentioned patent document 1, the structure which arrange | positions the heat insulating material comprised from the electroconductive raw material on the outer side of a 1st susceptor, and insulates with the heat insulating material so that the heat discharge | released from a susceptor may not leak out of an apparatus is disclosed. However, no mention is made of the heat generation of the insulation itself.

  Here, the choice of the material which comprises a heat insulating material has a restriction | limiting by the heat-resistant temperature of itself. That is, in an epitaxial apparatus in which a SiC thin film is deposited on a wafer by epitaxial growth, high-temperature growth is usually performed at a temperature exceeding 1800 ° C. Therefore, the heat insulating material is required to have heat resistance that can withstand use at such a high temperature. An example of a heat insulating material that satisfies such heat resistance is a carbon felt made of carbon fiber felt.

The specific resistance of carbon felt is 5 to 20 × 10 ⁻³ [Ω · m], which is sufficiently larger than the specific resistance of a heating element (susceptor) made of graphite. Since the heat generation of the heat insulating material itself made of such a material is not mentioned in Patent Document 1, in the technique disclosed in the same document, the heat insulating material whose specific resistance is sufficiently larger than that of the heat generating body is a conductor (heating resistance). It can be inferred that it was not considered at all.

  However, as a result of intensive research, the inventor has found that the local heat-up phenomenon in which the conductive heat insulating material made of carbon felt temporarily becomes much higher than the heating element made of graphite in the process of raising the temperature to a predetermined temperature. This was confirmed by temperature simulation using an appropriate experimental apparatus. Such a local overheating phenomenon of the heat insulating material does not appear remarkably in an equilibrium state at a high temperature of about 1800 ° C., and this causes the heat insulating material to be in a local overheating state during the temperature rising process in the conventional epitaxial apparatus. It is thought that this is the reason why he did not notice that he was.

  However, in the temperature rise process that cannot be avoided to reach a high temperature equilibrium state, it is necessary to prevent or suppress the occurrence of evaporation of the heating element itself made of graphite due to local overheating of the heat insulating material, albeit temporarily. In addition, it goes without saying that appropriate measures must be taken with respect to the heat resistance of the constituent material arranged outside the heat insulating material (in the case of Patent Document 1, a vacuum vessel mainly composed of a quartz tube). Here, the material forming the heating element is required to be a refractory metal material having a melting point higher than the maximum temperature during heat treatment, and the heating element is formed from a refractory metal material other than graphite. However, when the heat insulating material is formed of a material having a specific resistance higher than that of the refractory metal material, a local overheating phenomenon of the heat insulating material occurs in the temperature rising process.

  It should be noted that if the rate of temperature increase to a predetermined high temperature is set relatively slow, it is considered possible to suppress local overheating of the heat insulating material, but limiting the temperature increase rate to a predetermined rate or less This may be a factor that hinders the shortening of the temperature raising time for raising the temperature to a predetermined high temperature, which may lead to deterioration in production efficiency.

  The present invention finds for the first time a problem that has not been noticed without being noticed so far, and in order to solve this, a local overheating phenomenon in which the heat insulating material becomes much higher than the heating element in the temperature rising process. Suppressing and solving the evaporation problem of the heating element itself and the heat resistance problem of the components arranged outside the heat insulating material, shortening the heating time to raise the temperature to a predetermined high temperature and improving the production efficiency The object is to provide a feasible induction furnace.

  That is, the induction heating furnace of the present invention includes a heating chamber in which a heating object can be accommodated, and graphite having a melting point higher than the maximum temperature at the time of heat treatment for the heating object, and arranged so as to go around the outside of the heating chamber. Or a heating element formed from a refractory metal material, a conductive heat insulating material arranged to circulate around the outside of the heating element, a vacuum container arranged to circulate around the outside of the heat insulating material, and a vacuum container A coil wound around the outside, and as a heat insulating material, a material having a specific resistance larger than that of graphite or a refractory metal material constituting the heating element and applied in a circumferential direction by a slit is applied, The slit has a bent portion obtained by bending a predetermined portion by a predetermined angle with respect to the extending direction, and an outer peripheral side radially extending portion that is a portion on the outer peripheral side of the heat insulating material with respect to the bent portion. Peripheral radial extension Some or all of the portion over the outer circumferential side radially extending portion from the predetermined area closer to the part side, characterized in that packed the heat-resistant material which acts as an insulator.

Here, examples of the high melting point material forming the heating element include graphite, tungsten, tantalum, and alloys thereof.
If it is an induction heating furnace equipped with such a heat insulating material, in the process of raising the heating element to a predetermined high temperature by passing an electric current through the coil, the heat insulating material also heats up as the amount of heat increases, The eddy current that flows around the entire heat insulating material can be reduced to a smaller current than when there is no slit, preventing and suppressing the heat insulating material itself from heating up more rapidly than the heating element. The present inventor has confirmed that this is possible.

  Although the local overheating state of the heat insulating material in the temperature rising process has not been noticed so far, such a local overheating phenomenon causes the above-described problem, that is, evaporation of the high melting point material constituting the heating element and heat insulating material. Problems such as overheating of the member (vacuum container) arranged on the outside can be caused.

Therefore, in the induction heating furnace of the present invention, a conductive heat insulating material formed from a material having a sufficiently large specific resistance as compared with graphite or a refractory metal material constituting the heating element is considered as a conductor, In order to prevent the current flowing in the whole insulation material that increases with the amount of current flowing through the coil from following the circuit path, the insulation material is divided in the circumferential direction by the slit, and the slit itself contributes to the increase in resistance. The heat generation amount of the heat insulating material in the process is reduced, and the local overheating phenomenon of the heat insulating material can be prevented / suppressed. Also, by dividing the heat insulating material in the circumferential direction with slits, an area that defines the size of the electromotive force (induced electromotive force) generated in the conductive heat insulating material by electromagnetic induction (cross section perpendicular to the magnetic flux direction in the heat insulating material) ) Can be reduced by reducing this area, and by reducing the induced electromotive force, the amount of current flowing through the heat insulating material and the amount of heat generated by the heat insulating material are reduced, thereby preventing local overheating of the heat insulating material. -It can be suppressed.

  In the induction heating furnace of the present invention, in order to prevent the radiant heat of the heating element from leaking to the outside of the heat insulating material through the slit and to ensure the opening width of the slit, a heat resistant material is applied to a predetermined portion of the slit. It is preferable to adopt a packing configuration.

  The slit in the present invention may have any shape as long as it divides the heat insulating material in the circumferential direction, and examples thereof include a linear shape and a curved shape extending in the radial direction of the heat insulating material. In particular, when a predetermined portion of the slit extending in the radial direction of the heat insulating material is set to a bent portion bent at a predetermined angle with respect to the extending direction, the heat quantity and temperature of the radiation can be reduced by receiving the radiation of the heating element at the bent portion. It can reduce effectively and the situation where radiation leaks directly to the exterior of a heat insulating material can be avoided.

As described above, in the present invention, a conductive heat insulating material made of a material having sufficiently higher resistance than a heating element formed of graphite or a refractory metal material and capable of being locally overheated during a temperature rising process is provided with a heating resistance. By considering the body as a body and dividing the heat insulating material in the circumferential direction by slits, local overheating of the heat insulating material that occurs only at the time of temperature rise and does not appear remarkably in an equilibrium state can be prevented and suppressed. And if it is this invention induction heating furnace, since it can suppress the local overheating of a heat insulating material, it can heat up to desired temperature in a short time, without restricting a temperature rising rate, and shortens temperature rising time. As a result, it is possible to improve the production efficiency.

The typical sectional view of the induction heating furnace concerning one embodiment of the present invention. The figure which shows typically 90 degree | times (part equivalent to 1/4) of the circumferential direction among the experimental devices which verify the temperature change of the heat generating body applied to the induction heating furnace which concerns on the same embodiment, and a heat insulating material. The cross-sectional schematic diagram of the experimental apparatus of FIG. The figure which shows the temperature change of each point shown in FIG. 3 in the process of heating up the experimental apparatus of FIG. 2, and a high temperature equilibrium state. FIG. 4 is a diagram corresponding to FIG. 4 in the case of using a heat insulating material in which no slit is formed. The figure which shows the modification of the slit formed in the heat insulating material of the embodiment corresponding to FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, an induction heating furnace 1 according to the present embodiment includes a cylindrical heating chamber 2 that can accommodate a heating object W therein, and a cylindrical heating element 3 disposed around the heating chamber 2. And a conductive insulating material 4 having a substantially cylindrical shape arranged around the heating element 3, a vacuum vessel 5 arranged around the insulating material 4, and a coil 6 wound around the vacuum vessel 5. It is provided.

  The vacuum vessel 5 has a cylindrical shape and is configured such that gases (carrier gas, silicon source gas, carbon source gas, etc.) that are supplied into the room from the bottom inlet 51 and flow upward can be discharged from the upper outlet 52. is there. The gas passes through the inside of the heating chamber 2 and is exhausted from the exhaust port 52. A gas supply control valve 7 is connected to the air supply port 51 of the vacuum vessel 5 to adjust the gas supply amount into the vacuum vessel 5 and adjust the gas flow rate passing through the heating chamber 2. A pressure adjusting valve 8 capable of adjusting the pressure in the vacuum vessel 5 is connected to the exhaust port 52 of the gas tank, and each pressure adjusting device (not shown) connected to each of these valves (gas supply control valve 7 and pressure adjusting valve 8) The valves (the gas supply control valve 7 and the pressure adjusting valve 8) are controlled to adjust the pressure in the vacuum vessel 5 to a predetermined value.

  The coil 6 is an induction heating coil (high-frequency coil) arranged in a spiral shape so as to surround the vacuum vessel 5 at a position away from the outer wall of the vacuum vessel 5 by a predetermined distance. The coil 6 is connected to a power supply device (not shown) that can output AC power of an arbitrary frequency. By supplying AC power to the coil 6 from the power supply device, an alternating magnetic field is generated around the coil 6. Then, this alternating magnetic field is infiltrated into the permeation target and induction heating is performed.

The heating chamber 2 is a susceptor that is formed of graphite, which is a high melting point material having a higher melting point than the highest temperature during induction heating treatment, and is disposed at the center of the internal space of the vacuum vessel 5. It can be installed face-to-face. The heating chamber 2 is indirectly heated by heat (radiant heat) emitted from the heating element 3 heated by the coil 6. FIG. 1 shows an induction heating furnace 1 (vertical hot wall CVD epitaxial apparatus) in a state where a wafer is arranged as a heating object W inside the heating chamber 2.

  The heating element 3 is an integrally molded product formed of the same material as the heating chamber 2, that is, graphite which is a high melting point material, and the center of the axis is aligned with the center of the heating chamber 2, that is, the center of the internal space of the vacuum vessel 5. In this state, it is disposed outside the heating chamber 2.

  The heat insulating material 4 is disposed outside the heating element 3 with its axis center aligned with the center of the heating chamber 2, that is, the center of the internal space of the vacuum vessel 5, and is released from the heating element 3 heated by the coil 6. The function of blocking the heat so that it does not leak to the outside can be exhibited. The heat insulating material 4 has conductivity and heat resistance and is sufficiently larger than the high melting point material (graphite in this embodiment) forming the heating element 3 (hereinafter referred to as “specific resistance”). It is formed from a material having In this embodiment, the heat insulating material 4 formed with carbon felt is applied. The heat insulating material 4 and the heating element 3 are electrically insulated by appropriate means.

  And the slit S which divides this heat insulating material 4 in the circumferential direction is formed in the heat insulating material 4 which makes | forms a cylinder shape. The slit S has a linear shape extending in the radial direction from the inner peripheral edge of the heat insulating material 4 toward the outer peripheral edge, and is formed over the entire height direction of the heat insulating material 4. In the present embodiment, the slits S are formed at positions that divide the heat insulating material 4 into, for example, four equal parts in the circumferential direction. Each slit S has a shape extending radially from the center of the heat insulating material. The number of slits may be changed to an appropriate number in consideration of various factors such as the contents of treatment by the induction heating furnace 1, the shape of the heat insulating material 4, and the material. In addition, in FIG. 1, the cross section which passes along the slit S of the heat insulating material 4 (specifically heat-resistant material T mentioned later packed in the slit S) is shown.

  Here, if the part (partitioned part) divided | segmented by the slit S among the heat insulating materials 4 is caught as the "unit heat insulating material 4", the heat insulating material 4 of this embodiment will adjoin the circumferential direction through the slit S. FIG. It can be said that it has four unit heat insulating materials.

  Moreover, the heat insulating material 4 of this embodiment is filled with the heat-resistant material T excellent in fire resistance in the slit S, and the radiation of the heat generating body 3 passes directly through the slit S and is directly radiated to the outside. 5 and the coil 6) are prevented / suppressed. In FIG. 1, the heat-resistant material T is shown with an appropriate pattern. The heat-resistant material T functions as an insulator and also exhibits a slit width holding function for securing the opening width of the slit S. In the heat insulating material 4 of the present embodiment, the heat resistant material T is packed in the entire extending direction of the slit S extending in the radial direction of the heat insulating material 4 and in the entire height direction of the slit S. In the present embodiment, ceramics having excellent heat resistance and insulation are applied as the heat resistant material T. Examples of such ceramics include alumina, zirconia, and yttria.

  Moreover, although not shown in figure, the induction heating furnace 1 of this embodiment is equipped with the thermometer which measures the internal temperature of the heating chamber 2, and the output control apparatus which controls the output of the coil 6 based on the temperature measured with the thermometer. It is a thing.

  Next, the operation and effect of the induction heating furnace 1 having such a configuration will be described.

An alternating magnetic field is generated around the coil 6 by supplying AC power from the power supply device to the coil 6 in a state where the wafer W is installed at a predetermined position in the heating chamber 2. It penetrates into the heating element 3 made of a high melting point material (graphite in this embodiment), and the heating element 3 is induction heated. As a result, the heating chamber 2 is indirectly heated by the radiant heat of the heating element 3, and when the temperature in the heating chamber 2 reaches a predetermined target temperature (epitaxial growth temperature, for example, 1800 ° C.), the temperature is maintained. The output of the coil 6 (the output of the coil 6 according to the amount of AC power supplied from the power supply device to the coil 6) is controlled to maintain a high temperature equilibrium state. Further, the gas supply control valve 7 and the pressure adjustment valve 8 are controlled by the pressure adjustment device so that the pressure value in the vacuum vessel 5 becomes a predetermined value.

  By such processing, the induction heating furnace 1 according to the present embodiment forms a SiC thin film having a uniform thickness on the surface of the wafer W arranged in the heating chamber 2 in an equilibrium state of high temperature (about 1800 ° C.). be able to. Since the growth rate of the SiC thin film increases in proportion to the supply amount of the raw material gas, high-speed growth of the SiC thin film can be obtained by efficiently heating the gas and performing sufficient gas decomposition and supply. . That is, the induction heating furnace 1 according to this embodiment functions as a CVD epitaxial apparatus that realizes epitaxial growth for forming a SiC thin film on the wafer W, and produces an epitaxial wafer in which a SiC thin film is deposited on the wafer W by epitaxial growth. be able to.

  The induction heating furnace 1 of the present embodiment can stably supply a high-quality epitaxial wafer in which a SiC thin film whose thickness and impurity concentration are precisely controlled is deposited on the wafer W, and practical application of SiC semiconductor devices. Contribute to a lot.

  By the way, in the temperature raising process in which the heating element 3 is raised to a predetermined temperature, the heat insulating material 4 may be locally heated rather than the heating element 3 when heated at a certain rate of temperature rise.

  The local overheating phenomenon of the heat insulating material 4 in such a temperature rising process is caused by the heat insulating property and low density (low heat capacity) of the carbon felt constituting the heat insulating material 4, and in a high temperature equilibrium state, Compared to when the temperature rises, the amount of AC power supplied from the power supply device to the coil 6 is not reduced, and a rapid change in the amount of AC power supply does not occur. There are no major rises or major fluctuations. Here, in the case of heating slowly or in a heating state where the calorific value is small, the heat removal action by an appropriate cooling means functions effectively, so that the local overheating phenomenon of the heat insulating material 4 hardly occurs, while rapidly When heated or in a heated state where the amount of generated heat is large, the heat action exceeds the heat removal action because of the heat insulating material 4, and a local overheating phenomenon of the heat insulating material 4 occurs. Thus, the local overheating phenomenon of the heat insulating material 4 which does not occur in a high temperature equilibrium state and occurs only in the temperature rising process has not been particularly noticed and has not been regarded as a problem.

However, the local overheating phenomenon of the heat insulating material 4 in such a temperature rising process causes evaporation of the high melting point material (graphite in the present embodiment) constituting the heating element 3 and is disposed outside the heat insulating material 4. Excessive heat resistance may be required for the vacuum vessel 5 so that the vacuum vessel 5 does not overheat.

  Therefore, the induction heating furnace of the present embodiment applies the heat insulating material 4 divided in the circumferential direction by the slit S, increases the resistance due to the presence of the slit S, and insulates according to the AC power supply from the power supply device to the coil 6. The eddy current flowing in the material 4 does not pass through the slit S, so that the current is smaller than when the slit S does not exist.

  Then, the inventor measured the temperature at the observation point shown in FIG. 4 with a thermocouple using the experimental device X shown in FIG. 3, and the heat insulating material 4 was heated from the heating element 3 to be heated in the temperature rising process. It was confirmed by the measurement results shown in FIG.

In FIG. 3, in order to verify the temperature change during the heating process of the heating element 3 and the heat insulating material 4 in the induction heating furnace 1 of the present embodiment, the heating element 3 made of graphite or refractory metal (this embodiment) The heat insulating material 4 made of carbon felt divided in the circumferential direction by the slit S is arranged outside the cylindrical body Y made of graphite in the apparatus X, and a current is passed through the coil 6 wound outside the heat insulating material 4. FIG. 2 schematically shows 90 degrees in the circumferential direction (a portion corresponding to one-fourth in the circumferential direction) of an experimental apparatus X that can heat a columnar body Y made of graphite or refractory metal by induction heating. The licensed device X is a device for demonstrating that the temperature change in the heating process differs depending on the presence or absence of the slit S in the heat insulating material 4 made of carbon felt, and the maximum temperature during the heating treatment is about 1200 degrees. Since it is assumed, a glass fiber tape is applied as the heat-resistant material T.

FIG. 4 shows an example of temperature changes of the columnar body Y and the heat insulating material 4 made of graphite or refractory metal ( made of graphite in the present embodiment apparatus X) in the experimental apparatus X. The columnar body Y made of graphite or refractory metal and the heat insulating material 4 are in a state of being insulated from each other by appropriate means.

Here, the solid line shown in FIG. 4 is a line showing the temperature change of the graphite or refractory metal cylinder Y (point A) in FIG. 3, and the dotted line shown in FIG. 4 is the heat insulating material 4 in FIG. 4 is a line showing the temperature change at point B, the two-dot chain line shown in FIG. 4 is a line showing the temperature change at point C in the heat insulating material 4 in FIG. 3, and the one-dot chain line shown in FIG. It is a line which shows the temperature change of D point among the heat insulating materials 4 in FIG. Of the points B, C, and D of the heat insulating material 4, the point closest to the coil 6 is the point D, and the point farthest from the coil 6 is the point B. In addition, the numerical value in FIG. 3 is the dimension (unit is mm) between each member and the point of the experimental apparatus X.

Here, as a comparative example, heating was performed in an experimental apparatus having a configuration in accordance with the experimental apparatus X described above, in which a slit S was not formed as the heat insulating material 4 and a well-known one continuous in a ring shape was applied. FIG. 5 shows a temperature change example of the graphite or refractory metal cylinder and the heat insulating material. Here, each line shown in FIG. 5 is a line corresponding to each line shown in FIG.

As can be understood from FIG. 5, in the process of raising the temperature of the graphite or refractory metal cylinder that is the heating element, the heat insulating material made of carbon felt without slits is made of graphite or high It is heated before the cylindrical body made of a melting point metal, and the temperature rises more rapidly than the cylindrical body, resulting in a locally overheated state.

Thus, when carbon felt is used as a heat insulating material, the heat insulating body is heated prior to the heating element made of graphite or refractory metal to be heated, and the heat insulating material itself is locally heated. There is a concern that even a structural body (vacuum container) in contact with or close to the material will be in an overheated state.

On the other hand, as can be understood from FIG. 4, in the experimental apparatus X to which the insulating material 4 divided in the circumferential direction by the slit S is applied, the temperature of the graphite or refractory metal cylinder Y that is the heating element 3 is increased. In the process, the temperature of the heat insulating material 4 made of carbon felt divided in the circumferential direction by the slits S is also raised, and the degree of the temperature rise is the same as that of the graphite or refractory metal cylinder Y that is the heating element 3, It has been found that it is possible to avoid a situation in which only the heat insulating material 4 becomes much hotter than the heating element 3 and locally falls into an overheated state.

Therefore, by applying the heat insulating material 4 having such a temperature rising characteristic to the induction heating furnace 1, a local overheating state of the heat insulating material 4 in the temperature rising process can be prevented, and the heating element 3 is configured. It is possible to prevent / suppress the evaporation of graphite or refractory metal and the overheating phenomenon of the vacuum vessel 5 disposed outside the heat insulating material 4.

  As described above, the induction heating furnace 1 according to the present embodiment has a problem that has not been noticed until now, that is, the temperature of the induction heating furnace 1 because the calorific value is small in a high temperature equilibrium state. Paying attention to the local overheating phenomenon of the heat insulating material 4 that affects the temperature distribution of the induction heating furnace 1 in the temperature rising process in which the calorific value is increased, while hardly affecting the distribution, the heat insulating material 4 is circumferentially formed by the slits S. This local overheating phenomenon can be prevented / suppressed by adopting a structure that divides into two. As a result, evaporation of the heating element 3 itself in the temperature rising process and the heat resistance problem of the constituent material (vacuum vessel 5) arranged outside the heat insulating material 4 can be solved at a high temperature, and the temperature is raised to a predetermined high temperature. Even when the heating rate to be set is set fast, the local overheating phenomenon of the heat insulating material 4 can be prevented / suppressed, the heating time can be shortened, and as a result, a SiC film that grows at high speed on the wafer W can be obtained. The production process can be shortened, that is, the production efficiency can be improved.

  In particular, in this embodiment, since the heat-resistant material T is packed in the slit S, the heat-resistant material T can prevent / suppress the situation where the radiation of the heating element 3 leaks around the heat insulating material 4 through the slit S. At the same time, the interval between the slits S can be maintained. Furthermore, since the heat-resistant material T functions as an insulator, the resistance of the portion where the slits S are formed is further increased, and the eddy current that attempts to circulate the entire heat-insulating material 4 can be reliably blocked by the heat-resistant material T. It is possible to secure a good insulation state in the slit S portion.

  In addition, this invention is not limited to embodiment mentioned above. For example, in the above-described embodiment, the mode in which the heat insulating material is divided in the circumferential direction by a slit extending linearly (in a straight line in plan view) along the radial direction of the heat insulating material is illustrated. A slit S having a zigzag shape or a combination of these in a suitable manner (for example, the inner peripheral side portion of the heat insulating material in the slit is linear and the outer peripheral side portion is curved) may be employed.

  Further, as shown in FIG. 6, the heat insulating material 4 is formed by the slit S set at a bent portion S <b> 1 in which a predetermined portion of the slit S extending along the radial direction of the heat insulating material 4 is bent at a predetermined angle with respect to the extending direction. The structure which divides | segments in the circumferential direction may be sufficient. In the case of the slit S having such a bent portion S1, the radiation of the heating element 3 that has passed through the straight portion S2 of the slit S and reached the bent portion S1 hits the bent portion S1. Therefore, it is possible to prevent the radiation of the heating element 3 from leaking directly to the outside of the heat insulating material 4. That is, the bent portion S1 itself functions as a radiation shielding unit that shields radiation leakage.

  Furthermore, as shown in FIG. 6, if a configuration in which the heat-resistant material T is packed in the bent portion S1 of the slit S is adopted, the slit width in the bent portion S1 can be secured, and the presence and the presence of the bent portion S1 are compatible. As a result, radiation leakage can be prevented more reliably.

  Here, the heat-resistant material may be arranged so as to fill the entire area of the slit as shown in the above-described embodiment, but may be arranged so as to pack only a predetermined portion of the slit.

  In particular, as shown in FIG. 6, the slit S includes a bent portion S1, a radially extending portion S2 on the inner peripheral side of the heat insulating material 4 with respect to the bent portion S1, and an outer peripheral side of the heat insulating material 4 with respect to the bent portion S1. In the case of having the radially extending portion S3, the radiation of the heating element 3 that passes through the radially extending portion S2 on the inner circumferential side, the bent portion S1, and the radially extending portion S3 on the outer circumferential side, Since the temperature decreases by reaching and reaching the bent portion S1 from the radially extending portion S2, the outer peripheral side radially extending portion of the heat-resistant material T from a predetermined region of the bent portion S1 that is closer to the outer radially extending portion S3 side. It is desirable to pack the portion over the portion S3, that is, the portion that is irradiated with radiation whose temperature has decreased. Furthermore, if this heat-resistant material is made of an insulating material, radiation can be prevented from leaking directly to the outside, and an insulating state of the slit portion can be secured. The radially extending portion on the inner peripheral side and the radially extending portion on the outer peripheral side of the slit may have a shape other than a linear shape.

  As the heat-resistant material, ceramics were used in the induction heating furnace described above, and glass fiber tape was used in the experimental apparatus described above. However, the heat-resistant material is capable of maintaining physical properties even when exposed to high temperatures during induction heat treatment. Any heat-resistant material may be used as long as it is present.

  Moreover, if the slit width holding means that can ensure the opening width of the slit is realized by an appropriate member or mechanism other than the heat resistant material, the heat resistant material can be omitted. If the heat-resistant material is omitted, radiation that leaks to the outside of the heat insulating material through the slit is increased by the amount that does not pass through the heat-resistant material, and there is no component (vacuum container) to be placed outside the heat insulating material. The situation where it is heated easily is considered. In this case, it is possible to prevent / suppress the situation of overheating by providing a conduit for circulating a coolant for cooling the vacuum vessel in the vacuum vessel or on the inner wall or outer wall of the vacuum vessel.

  Moreover, although the aspect which divides a heat insulating material into 4 equal to the circumferential direction by the slit was illustrated in embodiment mentioned above, you may change the division | segmentation number of a heat insulating material by increasing / decreasing the number of slits suitably. Here, the number of divisions of the heat insulating material (the number of “unit heat insulating materials” (parts divided and divided by the slits) in the above-described embodiment) is the same as the number of slits. In addition, when only one slit is formed, the number of divisions of the heat insulating material becomes zero. In this case, if the number of divisions is regarded as 1, the relationship in which the number of slits and the number of divisions of the heat insulating material are the same is maintained. .

  In addition, the induction heating furnace may perform an appropriate treatment using a chemical reaction on the object to be heated, or may perform an appropriate treatment using sintering or melting on the object to be heated. It may be applied.

The object to be heated may be other than a wafer. In addition, the material constituting the heating element may be graphite or a refractory metal material having a melting point higher than the maximum temperature at the time of heat treatment on the object to be heated. In addition to graphite, tungsten, tantalum, molybdenum, niobium, or These alloys can be mentioned. The heat insulating material may also be made of a material having a specific resistance larger than that of graphite or refractory metal material constituting the heating element, and may be other than carbon felt.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Induction heating furnace 2 ... Heating chamber 3 ... Heat generating body 4 ... Heat insulating material 5 ... Vacuum container 6 ... Coil S ... Slit S1 ... Bending part T ... Heat-resistant material W ... Wafer (heating object)

Claims (1)

A heating chamber capable of accommodating a heating object inside;
A heating element formed from graphite or a refractory metal material, which is arranged so as to circulate around the outside of the heating chamber and has a melting point higher than the highest temperature during the heat treatment for the heating object;
A conductive heat insulating material arranged to circulate around the outside of the heating element;
A vacuum vessel arranged to circulate around the outside of the heat insulating material;
An induction heating furnace comprising a coil wound around the outside of the vacuum vessel,
The heat insulating material is formed from a material having a larger specific resistance than graphite or a refractory metal material constituting the heating element, and is divided in a circumferential direction by a slit,
The slit has a bent portion obtained by bending a predetermined portion by a predetermined angle with respect to the extending direction, and an outer peripheral radial extending portion that is a portion on the outer peripheral side of the heat insulating material with respect to the bent portion,
A heat-resistant material that functions as an insulator is packed in a part or all of a portion extending from a predetermined region of the bent portion toward the outer peripheral radial extension portion to the outer peripheral radial extension portion. Induction heating furnace.

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